Systems such as attenuators and Digital-to-Analog Convertors (DAC) often suffer from phase variations in the output when the attenuation value or digital scaling is changed. Generally, typical systems have sufficient tolerance built-in to accommodate for minor phase variations; however, for applications such as electronic warfare, surveillance, missile systems, synthetic aperture radars, software radio and for others, even minor change in signal phase can significantly degrade the overall system performance. To address needs of such applications, systems are designed to exhibit minimal phase variation; however, it is very challenging to accurately measure the effective minor phase change of an output signal, unless the system fails to perform as intended.
When input signals get attenuated for various reasons in a system, the attenuation process not only changes the amplitude but also varies the phase of output signals. Because amplitude and phase vary together in the output signal, they cannot be accurately separated and measured for system performance. To measure minor phase variation generally requires specialized and expensive (e.g. typical cost >$100 k) Testers, and oscilloscopes, which limit the ability to use off the shelf, low-cost automated test equipment (ATE).